Washington -LRB- CNN -RRB- -- President Barack Obama has approved the use of armed Predator drones in Libya , Defense Secretary Robert Gates said Thursday .

Gates suggested that the unmanned Predator missions may have already begun . He said he believed that the first flights were launched Thursday but were called back due to poor weather .

`` The president has said that where we have some unique capabilities , he is willing to use those , '' Gates said . `` And I think that today may in fact have been their first mission . ''

Gates said the Predator drones offer a `` modest contribution '' to NATO efforts to support rebels fighting embattled Libyan leader Moammar Gadhafi 's forces there , though Gadhafi is not a specific target .

Unmanned aerial vehicles offer more precise targeting , because their low-flying capability allows for better visibility , `` particularly on targets now that have started to dig themselves into defensive positions , '' Gates said .

He said the drones are needed for humanitarian reasons , and they have capabilities that larger aircraft such as A-10s and C-130s can not provide .

Vice Joint Chiefs Chairman Gen. James Cartwright said the added precision is necessary because forces loyal to Gadhafi `` nestle up in crowded areas '' to maximize civilian casualties .

`` It 's very difficult to identify friend from foe , '' Cartwright said , noting that the drones facilitate identification of individuals on the ground .

Remote Predator operators are now permitted to strike Gadhafi 's defense missions , including air defense , missile and radar sites . Predator strikes are also authorized for civilian protection and can hit Gadhafi 's troops , military installations and equipment in the field .

The U.S. employed the use of unmanned drones early in the NATO campaign , but they were intended for surveillance only and not authorized to fire .

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NEW : `` I think that today may in fact have been their first mission , '' Robert Gates says

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NEW : Vice Joint Chiefs chair says drones help distinguish `` friend from foe ''

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NEW : Gadhafi loyalists `` nestle up in crowded areas , '' Gen. James Cartwright says

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NEW : Air defense , missile and radar sites , as well as troops , are authorized targets